USFS National Forest System Trails · Helena-Lewis and Clark National Forest · Montana · Updated June 2026
South Fork Judith River (USFS trail 439) is a 6.5 mi trail in Helena-Lewis and Clark National Forest, Montana. Mountain bikes are designated as allowed year-round, with Class 1 e-bikes also designated.
Can I bike South Fork Judith River?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Allowed | year-round |
| Class 1 e-bike (pedal-assist, 20 mph) | Allowed | year-round |
| Class 2 e-bike (throttle, 20 mph) | Allowed | year-round |
| Class 3 e-bike (pedal-assist, 28 mph) | Allowed | year-round |
Zooming out: across Helena-Lewis and Clark National Forest, 91% of rideable trail miles are open to mountain bikes — a Bike Access Grade of A.
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About this trail
In Helena-Lewis and Clark National Forest, Montana, South Fork Judith River (USFS trail 439) covers 6.5 mi of National Forest System trail. This profile summarizes what the official US Forest Service trail record says about riding it: how long the trail is, what it's built on, how steep the route grades out, and which forms of bike use the agency has designated. USFS records list its surface as native material. No grade band is recorded, so a steepness-based difficulty isn't available for this trail. Mountain bikes are allowed, open year-round in the data. On the electric side, Class 1, Class 2, Class 3 e-bikes are also designated — Class 1 being pedal-assist only, Classes 2 and 3 adding a throttle and higher assisted speed. The route is mapped as USFS Trail Class 3 on the agency's 1-to-5 development scale, where 1 is the most primitive, minimally maintained tread and 5 is the most developed. Because conditions, closures, and local orders change between data refreshes, confirm the current status with the managing ranger district before you ride.
Frequently asked questions
- Can you mountain bike on South Fork Judith River?
- Yes. Mountain bikes are designated as allowed on South Fork Judith River in Helena-Lewis and Clark National Forest, year-round, per USFS data.
- Are e-bikes allowed on South Fork Judith River?
- Class 1, Class 2, Class 3 e-bikes are designated on South Fork Judith River in the USFS data.
- How long is South Fork Judith River?
- South Fork Judith River measures about 6.5 mi in total, summed across its mapped National Forest System segments.
- What is the surface of South Fork Judith River?
- USFS data records the tread surface of South Fork Judith River as native material.
How we read this data
Grade-based difficulty above is the USFS grade (route steepness), not a technical mountain-bike rating — a gentle-grade trail can still be rocky or technical, and vice versa. Bike and e-bike status come verbatim from the USFS managed-use fields for this trail; we never infer access we can't cite. See our methodology for how the dataset is built and what each field means.
Where it is
Approximate location of Helena-Lewis and Clark National Forest (USFS trail geometry isn't mapped).
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